Selective etch for metal-containing materials

ABSTRACT

Methods of selectively etching metal-containing materials from the surface of a substrate are described. The etch selectively removes metal-containing materials relative to silicon-containing films such as silicon, polysilicon, silicon oxide, silicon germanium and/or silicon nitride. The methods include exposing metal-containing materials to halogen containing species in a substrate processing region. A remote plasma is used to excite the halogen-containing precursor and a local plasma may be used in embodiments. Metal-containing materials on the substrate may be pretreated using moisture or another OH-containing precursor before exposing the resulting surface to remote plasma excited halogen effluents in embodiments.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No.61/903,240 filed Nov. 12, 2013, and titled “SELECTIVE ETCH FORMETAL-CONTAINING MATERIALS” by Ingle et al., which is herebyincorporated herein in its entirety by reference for all purposes.

FIELD

This invention relates to selectively removing metal-containingmaterial.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e.g. apattern transfer process proceed. Such an etch process is said to beselective of the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedthat selectively remove one or more of a broad range of materials.

Dry etch processes are often desirable for selectively removing materialfrom semiconductor substrates. The desirability stems from the abilityto gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma excitation of ammonia and nitrogen trifluoride enables siliconoxide to be selectively removed from a patterned substrate when theplasma effluents are flowed into the substrate processing region. Remoteplasma etch processes have recently been developed to selectively removea variety of dielectrics relative to one another. However, relativelyfew dry-etch processes have been developed to selectively removemetal-containing materials.

SUMMARY

Methods of selectively etching metal-containing materials from thesurface of a substrate are described. The etch selectively removesmetal-containing materials relative to silicon-containing films such assilicon, polysilicon, silicon oxide, silicon germanium and/or siliconnitride. The methods include exposing metal-containing materials tohalogen containing species in a substrate processing region. A remoteplasma is used to excite the halogen-containing precursor and a localplasma may be used in embodiments. Metal-containing materials on thesubstrate may be pretreated using moisture or another OH-containingprecursor before exposing the resulting surface to remote plasma excitedhalogen effluents in embodiments.

Embodiments of the invention include methods of etching metal-containingmaterial. The methods include transferring a substrate into a substrateprocessing region of a substrate processing chamber. The substrateincludes the metal-containing material. The methods further includeflowing a halogen-containing precursor into a remote plasma regionfluidly coupled to the substrate processing region while forming aremote plasma in the remote plasma region to produce plasma effluents.The methods further include etching the metal-containing material fromthe substrate by flowing the plasma effluents into the substrateprocessing region through through-holes in a showerhead. The showerheadis disposed between the remote plasma region and the substrateprocessing chamber.

Embodiments of the invention include methods of etching aluminum oxide.The methods include transferring a substrate into a substrate processingregion of a substrate processing chamber. The substrate includes thealuminum oxide. The methods further include flowing a gas-phaseoxygen-and-hydrogen-containing precursor into the substrate processingregion. The gas-phase oxygen-and-hydrogen-containing precursor includesan OH group. The methods further include flowing a chlorine-containingprecursor into a remote plasma region fluidly coupled to the substrateprocessing region while forming a remote plasma in the remote plasmaregion to produce plasma effluents. The methods further include etchingthe aluminum oxide from the substrate by flowing the plasma effluentsinto the substrate processing region through through-holes in ashowerhead.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedembodiments may be realized by reference to the remaining portions ofthe specification and the drawings.

FIG. 1 is a flow chart of an aluminum oxide selective etch processaccording to embodiments.

FIG. 2 is a flow chart of an aluminum oxide selective etch processaccording to embodiments.

FIG. 3A shows a schematic cross-sectional view of a substrate processingchamber according to embodiments.

FIG. 3B shows a schematic cross-sectional view of a portion of asubstrate processing chamber according to embodiments.

FIG. 3C shows a bottom view of a showerhead according to embodiments.

FIG. 4 shows a top view of an exemplary substrate processing systemaccording to embodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

Methods of selectively etching metal-containing materials from thesurface of a substrate are described. The etch selectively removesmetal-containing materials relative to silicon-containing films such assilicon, polysilicon, silicon oxide, silicon germanium and/or siliconnitride. The methods include exposing metal-containing materials tohalogen containing species in a substrate processing region. A remoteplasma is used to excite the halogen-containing precursor and a localplasma may be used in embodiments. Metal-containing materials on thesubstrate may be pretreated using moisture or another OH-containingprecursor before exposing the resulting surface to remote plasma excitedhalogen effluents in embodiments.

In order to better understand and appreciate the invention, reference isnow made to FIG. 1 which is a flow chart of an aluminum oxide selectiveetch process 100 according to embodiments. The aluminum oxide may have avariety of stoichiometries which may be determined by the method offorming the aluminum oxide. Prior to the first etch operation, aluminumoxide is formed on a substrate. The aluminum oxide may be in the form ofa blanket layer on the substrate or it may reside in discrete portionsof a patterned substrate surface. In either case, the aluminum oxideforms exposed surfaces of the surface of the substrate. The substrate isthen delivered into a substrate processing region (operation 110). Inanother embodiment, the aluminum oxide may be formed after deliveringthe substrate to the processing region, for example, by treating exposedportions of aluminum to a reactive oxygen source.

A flow of boron trichloride is introduced into a remote plasma regionseparate from the processing region (operation 120). Other sources ofhalogen may be used to augment or replace the boron trichloride. Ingeneral, a halogen-containing precursor, a bromine-containing precursoror a chlorine-containing precursor may be flowed into the remote plasmaregion in embodiments. The halogen-containing precursor may include oneor more of atomic chlorine, atomic bromine, molecular bromine (Br₂),molecular chlorine (Cl₂), hydrogen chloride (HCl), hydrogen bromide(HBr), or boron trichloride (BCl₃) in embodiments. Thehalogen-containing precursor may be a boron-and-bromine-containingprecursor according to embodiments, such as boron tribromide (BBr₃),BBr(CH₃)₂ or BBr₂(CH₃). The halogen-containing precursor may be acarbon-and-halogen-containing precursor according to embodiments, suchas CBr₄ or CCl₄. The halogen-containing precursor may comprise boron, inembodiments, to further increase the etch selectivity relative to one ormore of silicon, silicon germanium, silicon oxide or silicon nitride.

The separate plasma region may be referred to as a remote plasma regionherein and may be within a distinct module from the processing chamberor a compartment within the processing chamber. The separate plasmaregion may is fluidly coupled to the substrate processing region bythrough-holes in a showerhead disposed between the two regions. Thehardware just described may also be used in all processes discussedherein.

The plasma effluents formed in the remote plasma region are then flowedinto the substrate processing region (operation 125) through thethrough-holes the showerhead separating the remote plasma region and thesubstrate processing region. Aluminum oxide on the substrate isselectively etched (operation 135) such that aluminum oxide may beremoved more rapidly than a variety of other materials. Without bindingthe claim coverage to the accuracy of hypothetical mechanisms, theselective removal of aluminum oxide (e.g. Al₂O₃) may proceed by (1)forming BCl₂* in the plasma effluents, (2) reacting BCl₂* with exposedsurfaces of Al₂O₃ to form Al_(x)O_(y)Cl_(z)+Al+Cl* and (3) reacting Aland Cl* to form AlCl₃. Al_(x)O_(y)Cl_(z) and AlCl₃ desorb from thesurface once they are formed and are therefore characterized asvolatile. The formation of B₂O₃ and B—Si complexes may enhance thealuminum oxide etch selectivity to silicon (e.g. poly), silicon nitrideand silicon oxide. The reactive chemical species and any processeffluents are removed from the substrate processing region and then thesubstrate is removed from the substrate processing region (operation145).

All etch processes disclosed herein may be used to remove a broad rangeof metal-containing materials and aluminum oxide is simply one example.Generally speaking, all disclosed etch processes may be used toselectively remove metal-containing materials such as metal, a metaloxide or a metal nitride according to embodiments. The metal-containingmaterials may be aluminum oxide, titanium oxide, titanium nitride,tantalum nitride, tungsten, tungsten oxide or cobalt in embodiments. Themetal-containing materials may comprise one or more of aluminum,titanium, tantalum, tungsten or cobalt. In these examples, aluminum,titanium, tantalum, tungsten and cobalt are the “metal” in themetal-containing materials because, in relatively pure form, eachconducts electricity.

The processes disclosed herein (FIG. 1 as well as FIGS. 2-3 to bediscussed shortly) display etch selectivities of metal-containingmaterials relative to a variety of other materials. The metal-containingmaterial may be selectively etched relative to a silicon-containing filmwhich may also be present as exposed regions on the substrate. The etchselectivity of a metal-containing material relative to silicon(including single crystal, polysilicon or amorphous silicon) may begreater than or about 10:1, greater than or about 15:1, greater than orabout 20:1 or greater than or about 25:1 in embodiments. The etchselectivity of a metal-containing material relative to silicon nitridemay be greater than or about 15:1, greater than or about 20:1, greaterthan or about 25:1 or greater than or about 30:1 in embodiments. Theetch selectivity of a metal-containing material relative to siliconoxide may be greater than or about 20:1, greater than or about 25:1,greater than or about 30:1 or greater than or about 50:1 in embodiments.The etch selectivity of a metal-containing material relative to silicongermanium may be greater than or about 20:1, greater than or about 25:1,greater than or about 30:1 or greater than or about 50:1 in embodiments.High etch selectivities of metal-containing materials relative to thesematerials are helpful in creating a variety of devices by, for example,allowing aluminum oxide to be removed more conformally from sidewalls oftrench structures.

In embodiments, the halogen-containing precursor (e.g. BCl₃) is suppliedat a flow rate of between about 5 sccm and about 500 sccm, between about10 sccm and about 300 sccm, between about 25 sccm and about 200 sccm,between about 50 sccm and about 150 sccm or between about 75 sccm andabout 125 sccm.

The method also includes applying energy to the halogen-containingprecursor in the remote plasma region to generate the plasma effluents.The plasma may be generated using known techniques (e.g., radiofrequency excitations, capacitively-coupled power, inductively coupledpower). In an embodiment, the energy is applied using acapacitively-coupled plasma unit. The remote plasma source power may bebetween about 100 watts and about 3000 watts, between about 200 wattsand about 2000 watts, between about 300 watts and about 1000 watts inembodiments.

A low-intensity plasma may be applied (concurrently with the remoteplasma) in the substrate processing region to create a low ion densityand direct the low ion-density towards the substrate to accelerate theremoval rate of the aluminum oxide. A plasma in the substrate processingregion may also be referred to as a local plasma or a direct plasma. Thelow-intensity plasma in the substrate processing region may be appliedcapacitively, in embodiments, and will be referred to herein as a biasplasma because ions are being directed towards the substrate. The biasplasma may be applied with a bias power which is less than about 20% ofthe remote plasma power, less than about 10% of the remote plasma poweror less than about 5% of the remote plasma power in embodiments. Inembodiments, the bias power may be less than or about 100 watts, lessthan or about 75 watts, less than or about 50 watts, less than or about25 watts or essentially no bias power. The term “plasma-free” will beused herein to describe the substrate processing region duringapplication of essentially no bias power. The high neutral radicaldensity enables such a low bias power to be used productively to etchmetal-containing materials.

Reference is now made to FIG. 2 which is a flow chart of an aluminumoxide selective etch process 200 according to embodiments. The varioustraits and process parameters discussed with reference to FIG. 1 may notbe repeated here except when they deviate from those traits and processparameters.

A substrate is delivered into a substrate processing region (operation210) and aluminum oxide is formed on the surface or already presentbefore delivery. Moisture (H₂O in the form of water vapor) is introducedinto the substrate processing region (operation 220) and reacts withexposed surfaces of aluminum oxide on the surface of the substrate.Exposing aluminum oxide to moisture may result in the formation ofAl(OH)₃ absorbed on the surface of the substrate. Ammonia (NH₃) may beconcurrently added to or present in the substrate processing region aswell to increase the rate of reaction between the aluminum oxide and themoisture. Maintaining a pressure greater than 0.5 Torr or 1.0 Torr mayavoid dehydration of the Al(OH)₃ absorbates.

A flow of chlorine (Cl₂) is then introduced into a remote plasma regionseparate from the substrate processing region (operation 225). Thechlorine (Cl₂) is excited in a remote plasma ignited within the remoteplasma region. Other sources of chlorine may be used to augment orreplace the molecular chlorine. In general, a chlorine-containingprecursor may be flowed into the remote plasma region in embodiments.The chlorine-containing precursor comprises one or more of atomicchlorine, molecular chlorine (Cl₂), hydrogen chloride (HCl), or borontrichloride (BCl₃) in embodiments.

The plasma effluents formed in the remote plasma region are then flowedinto the substrate processing region (operation 230). The plasmaeffluents may be flowed into the substrate processing region afteroperation 220 in embodiments. Aluminum oxide on the substrate isselectively etched (operation 235) such that aluminum oxide may beremoved more rapidly than a variety of other materials. The plasmaeffluents may be converting Al(OH)₃ to AlCl₃, a volatile chemicalspecies that readily desorbs from the surface. Following removal ofaluminum oxide, the reactive chemical species and any process effluentsare removed from the substrate processing region and then the substrateis removed from the substrate processing region (operation 245).

Generally speaking, a gas-phase oxygen-and-hydrogen-containing precursormay be used in place of the moisture, so long as the gas-phaseoxygen-and-hydrogen-containing precursor includes an OH group. Thegas-phase oxygen-and-hydrogen-containing precursor may be moisture inthe form of water vapor or an alcohol in embodiments. The substrateprocessing region may be purged of gas-phaseoxygen-and-hydrogen-containing precursor between operation 220 andoperation 230 in embodiments. In the general case, ammonia (NH₃) mayalso be concurrently added to or present in the substrate processingregion as well to increase the rate of reaction between the aluminumoxide and the gas-phase oxygen-and-hydrogen-containing precursor.

A low-intensity plasma may be applied to the oxygen-containing precursorin the substrate processing region to create a low ion density plasma toassist with the reaction which forms adsorbed Al(OH)₃ on the surface ofthe aluminum oxide. The low-intensity plasma in the substrate processingregion may be applied capacitively in embodiments. The low-intensityplasma power may be less than or about 100 watts, less than or about 75watts, less than or about 50 watts, less than or about 25 watts oressentially zero in embodiments. The term “plasma-free” used to describethe substrate processing region herein corresponds to applying no plasmapower to the gas-phase oxygen-and-hydrogen-containing precursor.Alternatively or in combination, the gas-phaseoxygen-and-hydrogen-containing precursor may be flowed through theremote plasma region and excited with a remote plasma. The remote plasmapower used to excite the gas-phase oxygen-and-hydrogen-containingprecursor may be less than or about 100 watts, less than or about 75watts, less than or about 50 watts, less than or about 25 watts oressentially zero in embodiments. In embodiments, the gas-phaseoxygen-and-hydrogen-containing precursor is not excited in any plasmabefore encountering the aluminum oxide of the substrate.

In embodiments, the gas-phase oxygen-and-hydrogen-containing precursoris supplied at a flow rate of between about 100 sccm and about 2 slm(standard liters per minute), between about 200 sccm and about 1 slm, orbetween 500 sccm and about 1 slm in embodiments. The chlorine-containingprecursor (e.g. Cl₂) may be supplied at a flow rate of between about 5sccm and about 500 sccm, between about 10 sccm and about 300 sccm,between about 25 sccm and about 200 sccm, between about 50 sccm andabout 150 sccm or between about 75 sccm and about 125 sccm inembodiments.

The method also includes applying energy to the chlorine-containingprecursor in the remote plasma region to generate the plasma effluents.The plasma may be generated using known techniques (e.g., radiofrequency excitations, capacitively-coupled power, and inductivelycoupled power). The remote plasma source power may be between about 100watts and about 3000 watts, between about 200 watts and about 2000watts, or between about 300 watts and about 1000 watts in embodiments.

Reference is now made to FIG. 3 which is a flow chart of an aluminumoxide selective etch process 300 according to embodiments. The aluminumoxide may have a variety of stoichiometries which may be determined bythe method of forming the aluminum oxide. Prior to the first etchoperation, aluminum oxide is formed on a substrate. The aluminum oxidemay be in the form of a blanket layer on the substrate or it may residein discrete portions of a patterned substrate surface. In either case,the aluminum oxide forms exposed surfaces of the surface of thesubstrate. The substrate is then delivered into a substrate processingregion (operation 310). In another embodiment, the aluminum oxide may beformed after delivering the substrate to the processing region, forexample, by treating exposed portions of aluminum to a reactive oxygensource.

A flow of boron tribromide (BBr₃) is introduced into the substrateprocessing region (operation 320). Other sources of halogen may be usedto augment or replace the boron tribromide. In general, ahalogen-containing precursor, a bromine-containing precursor or achlorine-containing precursor may be flowed into the remote plasmaregion in embodiments. The halogen-containing precursor may include oneor more of atomic chlorine, atomic bromine, molecular bromine (Br₂),molecular chlorine (Cl₂), hydrogen chloride (HCl), hydrogen bromide(HBr), or boron trichloride (BCl₃) in embodiments. Thehalogen-containing precursor may be a boron-and-bromine-containingprecursor according to embodiments, such as boron tribromide (BBr₃),BBr(CH₃)₂ or BBr₂(CH₃). The halogen-containing precursor may be acarbon-and-halogen-containing precursor according to embodiments, suchas CBr₄ or CCl₄. The halogen-containing precursor may comprise boron, inembodiments, to further increase the etch selectivity relative to one ormore of silicon, silicon germanium, silicon oxide or silicon nitride.

Aluminum oxide on the substrate is selectively etched (operation 330)such that aluminum oxide may be removed more rapidly than a variety ofother materials. The selective removal of aluminum oxide (e.g. Al₂O₃)may proceed by thermal means (without the assistance of a local orremote plasma exciting the boron tribromide) in embodiments. Thereaction and removal of aluminum oxide with BBr₃ is exothermic. Incontrast, the reaction of BBr3 with silicon is endothermic which enablesa high Al₂O₃:Si etch selectivity for aluminum oxide selective etchprocess 300. Unused BBr₃ and any process effluents are removed from thesubstrate processing region and then the substrate is removed from thesubstrate processing region (operation 340).

Again, all etch processes disclosed herein may be used to remove a broadrange of metal-containing materials and aluminum oxide is simply oneexample. Generally speaking, all disclosed etch processes may be used toselectively remove metal-containing materials such as metal, a metaloxide or a metal nitride according to embodiments. The metal-containingmaterials may be aluminum oxide, titanium oxide, titanium nitride,tantalum nitride, tungsten, tungsten oxide or cobalt in embodiments. Themetal-containing materials may comprise one or more of aluminum,titanium, tantalum, tungsten or cobalt. In these examples, aluminum,titanium, tantalum, tungsten and cobalt are the “metal” in themetal-containing materials because, in relatively pure form, eachconducts electricity. Etch selectivites were discussed previously andare not repeated here for the sake of brevity.

In embodiments, the halogen-containing precursor (e.g. BBr₃) is suppliedat a flow rate of between about 5 sccm and about 500 sccm, between about10 sccm and about 300 sccm, between about 25 sccm and about 200 sccm,between about 50 sccm and about 150 sccm or between about 75 sccm andabout 125 sccm.

The reactions may proceed thermally, excited only by the temperature ofthe substrate itself, according to embodiments. Alternatively, themethod may include applying energy to the halogen-containing precursorin a remote plasma region to generate plasma effluents, which are thenintroduced into the substrate processing region in embodiments. FIG. 1and associated discussion described details of just such an embodiment.Also alternatively, a local plasma may be used to excite thehalogen-containing precursor. In the embodiments which include a plasma,the plasma may be generated using known techniques (e.g., radiofrequency excitations, capacitively-coupled power, inductively coupledpower). In an embodiment, the energy is applied using acapacitively-coupled plasma unit for either the remote plasma or thelocal plasma. The remote plasma source power or the local plasma sourcepower may be between about 100 watts and about 3000 watts, between about200 watts and about 2000 watts, between about 300 watts and about 1000watts in embodiments. In embodiments which rely on the temperature ofthe substrate to effect the etching reaction, the term “plasma-free” maybe used herein to describe the substrate processing region duringapplication using no or essentially no plasma power.

The substrate temperatures described next apply to all the embodimentsherein. The substrate temperature may be between about 30° C. and about400° C. in embodiments. In embodiments, the temperature of the substrateduring the etches described herein is greater than or about 30° C.,greater than or about 50° C., greater than or about 100° C., greaterthan or about 150° C. or greater than or about 200° C. The substratetemperatures may be less than or about 400° C., less than or about 350°C., less than or about 325° C., less than or about 300° C., and may bebetween about 200° C. and about 300° C. in embodiments. These relativelylow temperatures may be used, in embodiments, for remote or local plasmaprocesses or etch processes that use carbon-containing precursors (e.g.CBr₄, CCl₄, BrB(CH₃)₂ or BrB₂(CH₃)) as etch precursors. Higher substratetemperatures may be used in embodiments which use select precursors(e.g. BBr₃) low-intensity plasma or no plasma to excite thehalogen-containing precursor. Therefore, generally speaking, thesubstrate temperature may be between about 30° C. and about 800° C. inembodiments. In embodiments, the temperature of the substrate during theetches described herein may be between about 30° C. and about 800° C.,between about 300° C. and about 800° C., preferably between about 400°C. and about 800° C., more preferably between about 500° C. and about800° C.

The process pressures described next apply to all the embodimentsherein. The pressure within the substrate processing region is below orabout 50 Torr, below or about 30 Torr, below or about 20 Torr, below orabout 10 Torr or below or about 5 Torr. The pressure may be above orabout 0.1 Torr, above or about 0.2 Torr, above or about 0.5 Torr orabove or about 1 Torr in embodiments. In a preferred embodiment, thepressure while etching may be between about 0.3 Torr and about 10 Torr.However, any of the upper limits on temperature or pressure may becombined with lower limits to form additional embodiments. Pressuresgreater than 0.5 Torr or 1.0 Torr may reduce dehydration of the chemicalintermediate, Al(OH)₃, in the embodiments described in connection withFIG. 2.

For some materials and precursor combinations, the etch rate may drop intime and benefit from etch-purge-etch and etch-purge-etch cycles. Thismay be the case for boron-containing precursors used to etch at leastaluminum oxide, but other materials may also display this effect.Therefore, the etching operations of all processes may have a pause inthe flow of precursors to either the remote plasma or into the substrateprocessing region during the processes disclosed and claimed herein. Theremote plasma region and/or the substrate processing region may beactively purged using a gas which displays essentially no chemicalreactivity to the exposed materials on the patterned substrate. Afterpurging the flows of precursors may be resumed to restart the removal ofmetal-containing material from the patterned substrate at a rejuvenatedor renewed etch rate (which may be the same or similar to the initialetch rate of the etch process).

Generally speaking, the processes described herein may be used to etchmetal-containing materials. In the case of aluminum oxide, the filmscontain aluminum and oxygen (and not just any specific example ofstoichiometric aluminum oxide). The remote plasma etch processes mayremove aluminum oxide which includes an atomic concentration of about20% or more aluminum and about 60% or more oxygen in embodiments. Thealuminum oxide may consist essentially of aluminum and oxygen, allowingfor small dopant concentrations and other undesirable or desirableminority additives, in embodiments. Aluminum oxide may have roughly anatomic ratio 2:3 (Al:O). The aluminum oxide may contain between 30% and50% aluminum and may contain between 50% and 70% oxygen in embodiments.

An advantage of the processes described herein lies in the conformalrate of removal of metal-containing material from the substrate. Themethods do not rely on a high bias power to accelerate etchants towardsthe substrate, which reduces the tendency of the etch processes toremove material on the tops and bottom of trenches before material onthe sidewalls can be removed. As used herein, a conformal etch processrefers to a generally uniform removal rate of material from a patternedsurface regardless of the shape of the surface. The surface of the layerbefore and after the etch process are generally parallel. A personhaving ordinary skill in the art will recognize that the etch processlikely cannot be 100% conformal and thus the term “generally” allows foracceptable tolerances.

In each remote plasma or local plasma described herein, the flows of theprecursors into the remote plasma region may further include one or morerelatively inert gases such as He, N₂, Ar. The inert gas can be used toimprove plasma stability, ease plasma initiation, and improve processuniformity. Argon is helpful, as an additive, to promote the formationof a stable plasma. Process uniformity is generally increased whenhelium is included. These additives are present in embodimentsthroughout this specification. Flow rates and ratios of the differentgases may be used to control etch rates and etch selectivity.

In embodiments, an ion suppressor as described in the exemplaryequipment section may be used to provide radical and/or neutral speciesfor selectively etching substrates. The ion suppressor may also bereferred to as an ion suppression element. In embodiments, for example,the ion suppressor is used to filter halogen-containing plasma effluentsto selectively etch aluminum oxide. The ion suppressor may be includedin each exemplary process described herein. Using the plasma effluents,an etch rate selectivity of metal-containing material to a wide varietyof materials may be achieved.

The ion suppressor may be used to provide a reactive gas having a higherconcentration of radicals than ions. The ion suppressor functions todramatically reduce or substantially eliminate ionically charged speciestraveling from the plasma generation region to the substrate. Theelectron temperature may be measured using a Langmuir probe in thesubstrate processing region during excitation of a plasma in the remoteplasma region on the other side of the ion suppressor. In embodiments,the electron temperature may be less than 0.5 eV, less than 0.45 eV,less than 0.4 eV, or less than 0.35 eV. These extremely low values forthe electron temperature are enabled by the presence of the showerheadand/or the ion suppressor positioned between the substrate processingregion and the remote plasma region. Uncharged neutral and radicalspecies may pass through the openings in the ion suppressor to react atthe substrate. Because most of the charged particles of a plasma arefiltered or removed by the ion suppressor, the substrate is notnecessarily biased during the etch process. Such a process usingradicals and other neutral species can reduce plasma damage compared toconventional plasma etch processes that include sputtering andbombardment. The ion suppressor helps control the concentration of ionicspecies in the reaction region at a level that assists the process.Embodiments of the present invention are also advantageous overconventional wet etch processes where surface tension of liquids cancause bending and peeling of small features.

In all the examples described herein, a hydrocarbon may be added to thehalogen-containing precursor in the remote plasma region. Thehydrocarbon may be an alkane of the form C_(x)H_(y) such as methane,ethane, ethane, propane and propene. Inclusion of a hydrocarbon in theprocess may make silicon surfaces more inert to the plasma effluents,further increasing the etch selectivity of the aluminum oxide etchprocesses described herein.

FIG. 3A shows a cross-sectional view of an exemplary substrateprocessing chamber 1001 with a partitioned plasma generation regionwithin the processing chamber. During film etching, a process gas may beflowed into chamber plasma region 1015 through a gas inlet assembly1005. A remote plasma system (RPS) 1002 may optionally be included inthe system, and may process a first gas which then travels through gasinlet assembly 1005. The process gas may be excited within RPS 1002prior to entering chamber plasma region 1015. Accordingly, thechlorine-containing precursor as discussed above, for example, may passthrough RPS 1002 or bypass the RPS unit in embodiments.

A cooling plate 1003, faceplate 1017, ion suppressor 1023, showerhead1025, and a substrate support 1065 (also known as a pedestal), having asubstrate 1055 disposed thereon, are shown and may each be includedaccording to embodiments. Pedestal 1065 may have a heat exchange channelthrough which a heat exchange fluid flows to control the temperature ofthe substrate. This configuration may allow the substrate 1055temperature to be cooled or heated to maintain relatively lowtemperatures, such as between −20° C. to 200° C. Pedestal 1065 may alsobe resistively heated to relatively high temperatures, such as between100° C. and 1100° C., using an embedded heater element.

Exemplary configurations may include having the gas inlet assembly 1005open into a gas supply region 1058 partitioned from the chamber plasmaregion 1015 by faceplate 1017 so that the gases/species flow through theholes in the faceplate 1017 into the chamber plasma region 1015.Structural and operational features may be selected to preventsignificant backflow of plasma from the chamber plasma region 1015 backinto the supply region 1058, gas inlet assembly 1005, and fluid supplysystem 1010. The structural features may include the selection ofdimensions and cross-sectional geometries of the apertures in faceplate1017 to deactivate back-streaming plasma. The operational features mayinclude maintaining a pressure difference between the gas supply region1058 and chamber plasma region 1015 that maintains a unidirectional flowof plasma through the showerhead 1025. The faceplate 1017, or aconductive top portion of the chamber, and showerhead 1025 are shownwith an insulating ring 1020 located between the features, which allowsan AC potential to be applied to the faceplate 1017 relative toshowerhead 1025 and/or ion suppressor 1023. The insulating ring 1020 maybe positioned between the faceplate 1017 and the showerhead 1025 and/orion suppressor 1023 enabling a capacitively coupled plasma (CCP) to beformed in the first plasma region.

The plurality of holes in the ion suppressor 1023 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 1023. For example,the aspect ratio of the holes, or the hole diameter to length, and/orthe geometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 1023 is reduced. The holes in the ion suppressor 1023 mayinclude a tapered portion that faces chamber plasma region 1015, and acylindrical portion that faces the showerhead 1025. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 1025. An adjustable electrical biasmay also be applied to the ion suppressor 1023 as an additional means tocontrol the flow of ionic species through the suppressor. The ionsuppression element 1023 may function to reduce or eliminate the amountof ionically charged species traveling from the plasma generation regionto the substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.

Plasma power can be of a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma maybe provided by RF power delivered to faceplate 1017 relative to ionsuppressor 1023 and/or showerhead 1025. The RF power may be betweenabout 10 watts and about 5000 watts, between about 100 watts and about2000 watts, between about 200 watts and about 1500 watts, or betweenabout 200 watts and about 1000 watts in embodiments. The RF frequencyapplied in the exemplary processing system may be low RF frequenciesless than about 200 kHz, high RF frequencies between about 10 MHz andabout 15 MHz, or microwave frequencies greater than or about 1 GHz inembodiments. The plasma power may be capacitively-coupled (CCP) orinductively-coupled (ICP) into the remote plasma region.

A precursor, for example a chlorine-containing precursor, may be flowedinto substrate processing region 1033 by embodiments of the showerheaddescribed herein. Excited species derived from the process gas inchamber plasma region 1015 may travel through apertures in the ionsuppressor 1023, and/or showerhead 1025 and react with an additionalprecursor flowing into substrate processing region 1033 from a separateportion of the showerhead. Alternatively, if all precursor species arebeing excited in chamber plasma region 1015, no additional precursorsmay be flowed through the separate portion of the showerhead. Little orno plasma may be present in substrate processing region 1033 during theremote plasma etch process. Excited derivatives of the precursors maycombine in the region above the substrate and/or on the substrate toetch structures or remove species from the substrate.

The processing gases may be excited in chamber plasma region 1015 andmay be passed through the showerhead 1025 to substrate processing region1033 in the excited state. While a plasma may be generated in substrateprocessing region 1033, a plasma may alternatively not be generated inthe processing region. In one example, the only excitation of theprocessing gas or precursors may be from exciting the processing gasesin chamber plasma region 1015 to react with one another in substrateprocessing region 1033. As previously discussed, this may be to protectthe structures patterned on substrate 1055.

FIG. 3B shows a detailed view of the features affecting the processinggas distribution through faceplate 1017. The gas distribution assembliessuch as showerhead 1025 for use in the processing chamber section 1001may be referred to as dual channel showerheads (DCSH) and areadditionally detailed in the embodiments described in FIG. 3A as well asFIG. 3C herein. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 1033 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 1025 may comprise an upper plate 1014 and a lower plate1016. The plates may be coupled with one another to define a volume 1018between the plates. The coupling of the plates may be so as to providefirst fluid channels 1019 through the upper and lower plates, and secondfluid channels 1021 through the lower plate 1016. The formed channelsmay be configured to provide fluid access from the volume 1018 throughthe lower plate 1016 via second fluid channels 1021 alone, and the firstfluid channels 1019 may be fluidly isolated from the volume 1018 betweenthe plates and the second fluid channels 1021. The volume 1018 may befluidly accessible through a side of the gas distribution assembly 1025.Although the exemplary system of FIGS. 3A-3C includes a dual-channelshowerhead, it is understood that alternative distribution assembliesmay be utilized that maintain first and second precursors fluidlyisolated prior to substrate processing region 1033. For example, aperforated plate and tubes underneath the plate may be utilized,although other configurations may operate with reduced efficiency or notprovide as uniform processing as the dual-channel showerhead asdescribed.

In the embodiment shown, showerhead 1025 may distribute via first fluidchannels 1019 process gases which contain plasma effluents uponexcitation by a plasma in chamber plasma region 1015. In embodiments,the process gas introduced into RPS 1002 and/or chamber plasma region1015 may contain chlorine, e.g., Cl₂ or BCl₃. The process gas may alsoinclude a carrier gas such as helium, argon, nitrogen (N₂), etc. Plasmaeffluents may include ionized or neutral derivatives of the process gasand may also be referred to herein as a radical-chlorine precursorreferring to the atomic constituent of the process gas introduced.

FIG. 3C is a bottom view of a showerhead 1025 for use with a processingchamber in embodiments. Showerhead 1025 corresponds with the showerheadshown in FIG. 3A. Through-holes 1031, which show a view of first fluidchannels 1019, may have a plurality of shapes and configurations tocontrol and affect the flow of precursors through the showerhead 1025.Small holes 1027, which show a view of second fluid channels 1021, maybe distributed substantially evenly over the surface of the showerhead,even amongst the through-holes 1031, which may help to provide more evenmixing of the precursors as they exit the showerhead than otherconfigurations.

The chamber plasma region 1015 or a region in an RPS may be referred toas a remote plasma region. In embodiments, the radical precursor, e.g.,a radical-chlorine precursor, is created in the remote plasma region andtravels into the substrate processing region where it may or may notcombine with additional precursors. In embodiments, the additionalprecursors are excited only by the radical-chlorine precursor. Plasmapower may essentially be applied only to the remote plasma region inembodiments to ensure that the radical-chlorine precursor provides thedominant excitation. Chlorine or another chlorine-containing precursormay be flowed into chamber plasma region 1015 at rates between about 5sccm and about 500 sccm, between about 10 sccm and about 150 sccm, orbetween about 25 sccm and about 125 sccm in embodiments.

Combined flow rates of precursors into the chamber may account for 0.05%to about 20% by volume of the overall gas mixture; the remainder beingcarrier gases. The chlorine-containing precursor may be flowed into theremote plasma region, but the plasma effluents may have the samevolumetric flow ratio in embodiments. In the case of thechlorine-containing precursor, a purge or carrier gas may be firstinitiated into the remote plasma region before the chlorine-containinggas to stabilize the pressure within the remote plasma region. Substrateprocessing region 1033 can be maintained at a variety of pressuresduring the flow of precursors, any carrier gases, and plasma effluentsinto substrate processing region 1033. The pressure may be maintainedbetween 0.1 mTorr and 100 Torr, between 1 Torr and 20 Torr or between 1Torr and 5 Torr in embodiments.

Embodiments of the dry etch systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 4 showsone such processing system (mainframe) 1101 of deposition, etching,baking, and curing chambers in embodiments. In the figure, a pair offront opening unified pods (load lock chambers 1102) supply substratesof a variety of sizes that are received by robotic arms 1104 and placedinto a low pressure holding area 1106 before being placed into one ofthe substrate processing chambers 1108 a-f. A second robotic arm 1110may be used to transport the substrate wafers from the holding area 1106to the substrate processing chambers 1108 a-f and back. Each substrateprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

The substrate processing chambers 1108 a-f may be configured fordepositing, annealing, curing and/or etching a film on the substratewafer. In one configuration, all three pairs of chambers, e.g., 1108a-f, may be configured to etch a film on the substrate, for example,chambers 1108 a-d may be used to etch the gapfill silicon oxide tocreate space for the airgap while chambers 1108 e-f may be used to etchthe polysilicon.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon” or “polysilicon”of the patterned substrate is predominantly Si but may include minorityconcentrations of other elemental constituents such as nitrogen, oxygen,hydrogen and carbon. Exposed “silicon” or “polysilicon” may consist ofor consist essentially of silicon. Exposed “silicon nitride” of thepatterned substrate is predominantly silicon and nitrogen but mayinclude minority concentrations of other elemental constituents such asoxygen, hydrogen and carbon. “Exposed silicon nitride” may consistessentially of or consist of silicon and nitrogen. Exposed “siliconoxide” of the patterned substrate is predominantly SiO₂ but may includeminority concentrations of other elemental constituents (e.g. nitrogen,hydrogen, carbon). In some embodiments, silicon oxide films etched usingthe methods disclosed herein consist essentially of silicon and oxygen.“Aluminum oxide” is predominantly aluminum and oxygen but may includeminority concentrations of other elemental constituents (e.g. nitrogen,hydrogen, carbon). Aluminum oxide may consist essentially of aluminumand oxygen. “Aluminum” is predominantly aluminum but may includeminority concentrations of other elemental constituents (e.g. nitrogen,hydrogen, oxygen, carbon). Aluminum oxide may consist essentially ofaluminum. Analogous definitions will be understood for othermetal-containing materials.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excited state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents (agas in an excited state which is exiting a plasma) which participate ina reaction to either remove material from or deposit material on asurface. “Radical-halogen” (or “radical-hydrogen”) are radicalprecursors which contain halogen (or hydrogen) but may contain otherelemental constituents. The phrase “inert gas” refers to any gas whichdoes not form chemical bonds when etching or being incorporated into afilm. Exemplary inert gases include noble gases but may include othergases so long as no chemical bonds are formed when (typically) traceamounts are trapped in a film.

The terms “gap” and “trench” are used throughout with no implicationthat the etched geometry has a large horizontal aspect ratio. Viewedfrom above the surface, trenches may appear circular, oval, polygonal,rectangular, or a variety of other shapes. A trench may be in the shapeof a moat around an island of material. The term “via” is used to referto a low aspect ratio trench (as viewed from above) which may or may notbe filled with metal to form a vertical electrical connection. As usedherein, a conformal etch process refers to a generally uniform removalof material on a surface in the same shape as the surface, i.e., thesurface of the etched layer and the pre-etch surface are generallyparallel. A person having ordinary skill in the art will recognize thatthe etched interface likely cannot be 100% conformal and thus the term“generally” allows for acceptable tolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described to avoid unnecessarily obscuringthe present invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

The invention claimed is:
 1. A method of etching aluminum oxide, themethod comprising: flowing a gas-phase oxygen-hydrogen-containingprecursor into the substrate processing region, wherein the gas-phaseoxygen-and-hydrogen-containing precursor comprises an OH group; flowinga halogen-containing precursor into a remote plasma region fluidlycoupled to the substrate processing region while forming a remote plasmain the remote plasma region to produce plasma effluents, wherein thehalogen-containing precursor comprises one or more precursors selectedfrom the group consisting of atomic chlorine, atomic bromine, molecularbromine (Br₂), molecular chlorine (Cl₂), hydrogen chloride (HCl),hydrogen bromide (HBr), boron tribromide (BBr₃), and boron trichloride(BCl₃); and etching the aluminum oxide from a substrate by flowing theplasma effluents into the substrate processing region throughthrough-holes in a showerhead, wherein the showerhead is disposedbetween the remote plasma region and the substrate processing chamber.2. The method of claim 1 wherein the halogen-containing precursorcontains one of boron or carbon.
 3. The method of claim 1 furthercomprising forming a local plasma in the substrate processing region. 4.A method of etching aluminum oxide, the method comprising: transferringa substrate into a substrate processing region of a substrate processingchamber, wherein the substrate comprises the aluminum oxide; flowing agas-phase oxygen-and-hydrogen-containing precursor into the substrateprocessing region, wherein the gas-phase oxygen-and-hydrogen-containingprecursor comprises an OH group; flowing a chlorine-containing precursorinto a remote plasma region fluidly coupled to the substrate processingregion while forming a remote plasma in the remote plasma region toproduce plasma effluents; and etching the aluminum oxide from thesubstrate by flowing the plasma effluents into the substrate processingregion through through-holes in a showerhead.
 5. The method of claim 4wherein the gas-phase oxygen-and-hydrogen-containing precursor reactswith the aluminum oxide to form Al(OH)₃ on the surface of the substrate.6. The method of claim 4 wherein the gas-phaseoxygen-and-hydrogen-containing precursor is purged from the substrateprocessing region before the operation of flowing the plasma effluentsinto the substrate processing region.
 7. The method of claim 4 whereinthe chlorine-containing precursor comprises one or more of atomicchlorine, molecular chlorine (Cl₂), hydrogen chloride (HCl), or borontrichloride (BCl₃).
 8. The method of claim 4 wherein a pressure in thesubstrate processing region is greater than 0.3 Torr during theoperation of flowing the gas-phase oxygen-and-hydrogen-containingprecursor into the substrate processing region.